Watts to Horsepower Converter (W ⇄ HP)

Convert watts to horsepower and horsepower to watts in one place. Supports mechanical HP, metric HP, and electrical HP with instant results, formulas, and examples.

Power Conversion Calculator

Mechanical HP is standard for engines and motors in the US.

Enter the power in watts to convert to horsepower.

Result updates automatically as you type.

Quick presets

Quick Watts to Horsepower Table

Watts (W) Mechanical HP Metric HP Electrical HP

How to convert watts to horsepower

Horsepower is a unit of power historically based on the power of a horse. Today, watts (W) are the SI unit of power, but horsepower is still widely used for engines, motors, and machinery.

Formulas

Mechanical horsepower (HP)

\( 1\ \text{HP}_{\text{mech}} = 745.6999\ \text{W} \)

Watts → HP (mechanical):
\( \text{HP}_{\text{mech}} = \dfrac{P_{\text{W}}}{745.6999} \)

HP → Watts (mechanical):
\( P_{\text{W}} = \text{HP}_{\text{mech}} \times 745.6999 \)

Metric horsepower (PS, CV, hk)

\( 1\ \text{HP}_{\text{metric}} = 735.49875\ \text{W} \)

Watts → HP (metric):
\( \text{HP}_{\text{metric}} = \dfrac{P_{\text{W}}}{735.49875} \)

HP → Watts (metric):
\( P_{\text{W}} = \text{HP}_{\text{metric}} \times 735.49875 \)

Electrical horsepower

\( 1\ \text{HP}_{\text{elec}} = 746\ \text{W} \)

Watts → HP (electrical):
\( \text{HP}_{\text{elec}} = \dfrac{P_{\text{W}}}{746} \)

HP → Watts (electrical):
\( P_{\text{W}} = \text{HP}_{\text{elec}} \times 746 \)

Worked example: 1500 W to HP

Convert 1500 watts to mechanical horsepower:

  1. Use the formula \( \text{HP}_{\text{mech}} = P_{\text{W}} / 745.6999 \).
  2. Substitute \( P_{\text{W}} = 1500 \): \( \text{HP}_{\text{mech}} = 1500 / 745.6999 \).
  3. Calculate: \( \text{HP}_{\text{mech}} \approx 2.011 \).

So a 1500 W device is roughly 2.01 HP (mechanical). In everyday language, this is usually called a 2 HP motor.

Mechanical vs metric vs electrical horsepower

Several slightly different definitions of horsepower are in use. The differences are small, but they matter in engineering and when comparing specifications from different regions.

  • Mechanical horsepower (HP): used mainly in the US and UK for engines and motors. Defined as exactly 550 ft·lbf/s, which equals 745.6999 W.
  • Metric horsepower (PS, CV, hk): used historically in Europe and some Asian countries. Defined as the power needed to lift a 75 kg mass at 1 m/s, equal to 735.49875 W.
  • Electrical horsepower: used for electric motor ratings, defined as exactly 746 W.

For most automotive and general-purpose calculations, mechanical horsepower is the safest default unless the documentation explicitly says otherwise (e.g., “PS” or “CV” for metric horsepower).

Common conversions

  • 1 HP (mechanical) ≈ 745.7 W
  • 1 HP (metric) ≈ 735.5 W
  • 1 HP (electrical) = 746 W
  • 1 kW ≈ 1.341 HP (mechanical)
  • 1 HP (mechanical) ≈ 0.746 kW

Example: HP to watts

Convert 5 HP (mechanical) to watts:

\( P_{\text{W}} = \text{HP}_{\text{mech}} \times 745.6999 = 5 \times 745.6999 = 3728.4995\ \text{W} \)

So 5 HP ≈ 3728.5 W, or about 3.73 kW.

FAQ

How do you convert watts to horsepower?

Divide the power in watts by the appropriate watts-per-horsepower factor. For mechanical horsepower, use:

\( \text{HP}_{\text{mech}} = \dfrac{P_{\text{W}}}{745.6999} \)

What is 1 horsepower in watts?

It depends on the definition:

  • 1 HP (mechanical) = 745.6999 W
  • 1 HP (metric) = 735.49875 W
  • 1 HP (electrical) = 746 W

Is horsepower the same as brake horsepower (bhp)?

Brake horsepower is a way of measuring horsepower at the engine’s output shaft using a dynamometer. The unit is still horsepower, but bhp is usually higher than wheel horsepower because it does not include drivetrain losses.

Why do some car specs use PS or CV instead of HP?

PS (Pferdestärke), CV (chevaux vapeur), and hk are regional names for metric horsepower. They are close to mechanical HP but not identical. 1 PS ≈ 0.9863 mechanical HP.

Which horsepower type should I use?

  • Use mechanical HP for most US/UK engine and motor ratings.
  • Use metric HP when specs explicitly say PS, CV, or hk.
  • Use electrical HP for detailed electrical engineering work where 746 W per HP is specified.